Combined Passive/Active Flow Control of Drag and Lift Forces on a Cylinder in Crossflow Using a Synthetic Jet Actuator and Porous Coatings

This paper combines a synthetic jet actuator (SJA) and a leeward porous coating to alter the aerodynamic forces on a cylinder in crossflow at Re = 4.2 x 10(4). While SJAs and porous coatings are known to be effective flow control methods in isolation, their combined effect has not been studied. A 2D numerical model was created of a cylinder with a SJA at 90 degrees and 100 degrees leeward porous coating. The model was validated using accompanying water tunnel tests. The combined model was tested for dimensionless frequencies 0.15 < f(+) < 4 and compared to reference models. For f(+) < 1, using only the SJA increases the cylinder drag coefficient (C-d). Combining a porous coating with the SJA in that regime lowers the C-d values by 15-21%, and causes an overall reduction in C-d compared to the smooth cylinder baseline case. However, using only the porous coating causes a superior 35% reduction in C-d. For f(+) > 1, the combined SJA and porous coating configuration did not differ from the SJA only configuration, achieving the largest drag reduction of 45% at f(+) = 4. The flow control mechanisms of the SJA and porous coating do not combine constructively in this current setup. However, the porous coating is beneficial for f(+) < 1, causing an overall drag reduction even when the active SJA tends to increase drag.

Automated summary

This study combines a synthetic jet actuator (SJA) and a leeward porous coating to modify the aerodynamic forces on a cylinder. The results show that the combination of SJA and porous coating can reduce the drag coefficient, especially when f(+) < 1. However, there is no significant advantage of the combined configuration when f(+) > 1. The use of porous coating alone is more effective.